A Gas Turbine Engine (GTE) can contain different combinations of bladed rotors, such as axial compressor, radial or centrifugal compressor, axial turbine, radial inflow turbine, and fan rotors. During GTE operation, the blades of the rotor are bathed in core gas flow and thus exposed to high temperature, chemically-harsh (e.g., corrosive and oxidative) environments. In contrast, the inner “hub disk” portion of the rotor is largely shielded from core gas flow, but subject to considerable mechanical stress resulting from the centrifugal forces acting on the rotor. Performance benefits can consequently be realized by fabricating the hub disk and rotor blades from different alloys tailored to their unique operating environments. For example, an inserted blade rotor can be produced by attaching bladed pieces composed of a first superalloy to a separately-fabricated hub disk composed of a different superalloy. The bladed pieces are fabricated to include shanks, which are inserted into mating slots provided around the outer rim of the hub disk. Prior to insertion of the blades, the hub disk may be subject to a differential heat treatment process during which the rim of the hub disk is heated, while the inner bore region of the hub disk is cooled relative to the rim. Such a differential heat treatment process promotes grain growth in the rim of the hub disk to increase compliance at the shank-disk interfaces for improved uniformity of load distribution during high speed rotation of the bladed rotor.
While enabling the production of a bladed rotor having blades and a hub disk fabricated from dissimilar alloys, the above-described inserted blade manufacturing approach is associated with multiple disadvantages. Precision machining of the mating shank-disk interfaces can increase the cost and duration of manufacture. If not adequately sealed, the mating shank-disk interfaces can permit undesired leakage across the rotor and potentially trap corrosive debris. As a further drawback, the formation of the shank-disk interfaces may necessitate an increase in the overall size and weight of the bladed rotor to achieve a structural integrity comparable to that of a single piece or monolithic rotor. More recently, manufacturing approaches have been developed for the production of a so-called “bonded dual alloy rotor,” such as a dual alloy turbine wheel or compressor wheel. In one approach for producing a bonded dual alloy turbine rotor, a full blade ring is first produced by bonding a number of individually-cast bladed pieces. The full blade ring is then bonded to a separately-fabricated hub disk by diffusion bonding, friction welding, or another bonding process. This yields a rotor having exceptional high temperature properties, a relatively compact and lightweight form factor, low leakage levels, and other desirable characteristics.
While providing multiple advantages over inserted blade rotors, bonded dual alloy rotors and the manufacturing approaches for producing such rotors remain limited in certain respects. For example, and without implying that others in the relevant field have recognized such limitations, the heat treatment processes conventionally performed when producing a bonded dual alloy rotor may fail to adequately create or preserve optimal high temperature properties of the rotor blades, the hub disk, and/or any coating present on the rotor blades. There thus exists an ongoing need for improved dual alloy rotor manufacturing processes, which overcome such limitations to yield a rotor having enhanced performance characteristics (e.g., high temperature capabilities) and a prolonged service lifespan. Such improved rotor manufacturing processes are disclosed herein.